Construction method of large-size bearing platform right above existing operating subway

Abstract

The invention relates to a construction method of a large-volume bearing platform right above an existing operating subway, and the construction of the large-volume bearing platform right above the existing operating subway is realized through the combination of technologies of driving short pile enclosures, controlling the reinforcement depth of a pit bottom soil body, dividing a cast-in-place bearing platform, casting the cast-in-place bearing platform and prefabricating the bearing platform and a rapid splicing technology of the bearing platform. By means of the construction method for the large-size bearing platform over the existing operating subway, damage to the structure of the existing operating subway in the bearing platform construction process can be avoided, and disturbance of bearing platform construction to the subway is greatly reduced; the conditions of subway shield floating, vibration breaking and the like are effectively prevented through combination of pile foundation uplift, cast-in-situ bearing platform and prefabricated bearing platform processes and a rapid bearing platform splicing process. And meanwhile, large-volume concrete pouring is avoided, the overall process is flexible and controllable, the bearing platform over the subway is rapidly constructed, and subsequent procedures are adjusted in time according to subway monitoring data.

Description

Technical Field

[0001] The invention relates to a large-volume foundation construction method, and in particular to a large-volume foundation construction method directly above an existing operating subway. Background Art

[0002] Since the beginning of the 21st century, my country's urbanization process has developed rapidly, and the infrastructure structure and scale of first-tier cities such as Beijing, Shanghai, Guangzhou and Shenzhen have changed with each passing day. Infrastructure construction has gradually developed from flat and extensive to three-dimensional and intensive. More and more newly built urban elevated roads inevitably have a large number of intersections and crossings with existing operating subways, especially in the central urban areas with busy traffic. The contradiction is particularly prominent.

[0003] Therefore, the number of new urban elevated bridges being built directly above existing operating subways is increasing, and most of them are large-volume concrete bridges. If effective protection measures are not taken and construction methods are not adjusted, the subway shield may float up or break during the bridge construction, seriously affecting the safety of existing subway operations and causing adverse social impacts.

[0004] In view of the above problems, a construction method is needed that can avoid damage to the existing operating subway structure during the construction of the cap and significantly reduce the disturbance of the cap to the subway. Measures such as pile foundation pull-out resistance, a combination of cast-in-place cap and prefabricated cap technology, and cap rapid splicing technology can be used to effectively prevent the floating of the subway shield and vibration breakage. At the same time, there is also a construction method that avoids large-volume concrete pouring, the overall process is flexible and controllable, the cap is quickly constructed above the subway, and the subsequent processes can be adjusted in time according to subway monitoring data. Summary of the invention

[0005] The present invention aims to provide a method for constructing a large-volume pedestal directly above an existing operating subway. By utilizing the method to construct a large-volume pedestal directly above an existing operating subway, damage to the existing operating subway structure during pedestal construction can be avoided and the disturbance of the subway to the subway caused by the pedestal construction can be greatly reduced. Measures such as pile foundation pull-out resistance, a combination of cast-in-place pedestal and prefabricated pedestal processes, and a pedestal rapid splicing process can be utilized to effectively prevent the subway shield from floating up, vibration breakage, and the like. At the same time, there are also advantages such as avoiding large-volume concrete pouring, flexible and controllable overall process, rapid construction of the pedestal directly above the subway, and timely adjustment of subsequent processes based on subway monitoring data.

[0006] In order to achieve the above-mentioned purpose, the technical scheme of the present invention is: a method for constructing a large-volume cap directly above an existing operating subway, which realizes the construction of a large-volume cap directly above an existing operating subway by using short piles for enclosure, controlling the depth of pit bottom soil reinforcement, combining cast-in-place caps with prefabricated caps, and a cap rapid splicing process. The specific steps are:

[0007] Step 1: Set up the detection device in the subway shield and collect the initial value;

[0008] Step 2: Construction of foundation pit support;

[0009] Step 3: Strengthen the bottom of the foundation pit;

[0010] Step 4: Cast the cap in batches outside the 1m range of the subway structure plane projection;

[0011] Step 5: Hoist the prefabricated cap within 1m of the plane projection of the subway structure;

[0012] Step 6: Wet joint construction of the foundation;

[0013] Step 7: The foundation is tensioned and backfilled in batches.

[0014] Preferably, in step 2, short piles are used for enclosure within 1 m of the plane projection of the subway structure to ensure that the length of the short piles is determined without affecting the operation of the existing subway. The enclosure piles can be one or more combinations of Larsen steel sheet piles, bored piles, SMW method piles, and MJS method piles according to the on-site conditions.

[0015] Preferably, in step 3, the plane range of the foundation pit bottom reinforcement is the entire foundation pit, so as to determine the soil reinforcement depth without affecting the operation of the existing subway. The soil reinforcement adopts MJS reinforcement, grouting or triaxial mixing piles according to the on-site conditions.

[0016] Preferably, in step 4, the pedestal outside the 1m range of the plane projection of the subway structure is divided into multiple pedestals from top to bottom, and the construction is carried out one by one in batches from bottom to top.

[0017] Preferably, in step 5, the pedestal within the 1m range of the plane projection of the subway structure is constructed by integral prefabrication and hoisting.

[0018] Preferably, in step 6, the cast-in-place cap and the prefabricated cap are quickly connected, the main reinforcement of the cap is fixed by welding through reserved U-shaped steel bars arranged crosswise, and Φ10 steel bars are passed through the middle. After the steel bars are welded and fixed, UHPC or high-strength concrete is used to construct the wet joint of the cap.

[0019] Preferably, the subway structure monitoring during the construction process adopts the arrangement of fully automatic vibration monitors inside the subway shield for vibration monitoring, and at the same time, data on shield settlement and convergence are regularly collected inside the subway shield. Based on the monitoring and collected data, timely feedback is provided and a series of response mechanisms such as data feedback, data analysis, and optimization of subsequent processes and technologies are established.

[0020] The beneficial effects of the present invention are:

[0021] The present invention proposes a method for constructing a large-volume foundation directly above an existing operating subway. Compared with the prior art, the present invention has the following improvements:

[0022] 1) By adopting measures such as short pile enclosure, controlling the soil reinforcement depth, and prefabricating and hoisting the entire cap above the subway, the disturbance to the existing operating subway during the cap construction process can be reduced.

[0023] 2) Dividing the cast-in-place foundation into multiple foundation blocks can reduce the difficulty of construction, utilize the pull-out resistance of the pile foundation, greatly shorten the impact of soil unloading above the subway, and prevent the subway from floating.

[0024] 3) The use of U-shaped reinforcement in the foundation and the rapid wet joint connection process can shorten the foundation construction period and reduce the impact on the existing operating subway.

[0025] The present invention can avoid the damage to the existing operating subway structure during the construction of the foundation and greatly reduce the disturbance of the foundation to the subway through the construction method. It can effectively prevent the subway shield from floating up, vibration and breakage by utilizing the pile foundation pull-out resistance, the combination of cast-in-place foundation and prefabricated foundation technology and the foundation rapid splicing technology. It also has the advantages of avoiding large-volume concrete pouring, flexible and controllable overall process, rapid construction of the foundation directly above the subway, and timely adjustment of subsequent processes according to subway monitoring data. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a diagram showing the relationship between the existing operating subway and the construction of the present invention;

[0027] Figure 2 This is a schematic diagram of Larsen steel sheet pile construction;

[0028] Figure 3 This is a schematic diagram of the pit bottom reinforcement construction;

[0029] Figure 4 This is a schematic diagram of cast-in-place cap construction;

[0030] Figure 5 This is a schematic diagram of the prefabricated foundation construction;

[0031] Figure 6 This is a schematic diagram of the wet joint construction of the cap;

[0032] Figure 7 It is the plan view of the wet joint of the cap;

[0033] Figure 8 This is the elevation drawing of the wet joint of the cap;

[0034] Fig. 9 It is a plan view of the layout of the detection equipment inside the subway shield during the construction of the foundation;

[0035] In the picture: 1. Existing operating subway shield, 2. Bored piles, 3. Larsen steel sheet piles, 4. Pit bottom reinforcement, 5. Cast-in-place cap, 6. Precast cap, 7. Cap wet joint, 8. Wet joint steel bars, 9. UHPC, 10. Fully automated vibration monitor inside subway shield. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and examples.

[0037] like Figures 1 to 9 As shown, the method for constructing a large-volume foundation directly above an existing operating subway of the present invention comprises the following steps:

[0038] Step 1: Set up a detection device in the existing operating subway shield 1 and collect initial values.

[0039] Step 2: Construction of foundation pit support, see attached Figure 2 .

[0040] Short piles are used for enclosure within 1m of the plane projection of the subway structure to ensure that the existing subway operation is not affected. The length of the short piles is determined, and the remaining enclosure piles are of regular length. The enclosure piles can be in one or more combinations of Larsen steel sheet piles 3, bored cast-in-place piles 2, SMW method piles, MJS method piles, etc. according to the on-site conditions.

[0041] Step 3: Pit bottom reinforcement 4, see attached Figure 3 .

[0042] The 4-plane range of the foundation pit bottom reinforcement is the entire foundation pit, so as to determine the soil reinforcement depth without affecting the existing subway operation. The soil reinforcement can be carried out in the form of MJS reinforcement, grouting or triaxial mixing piles according to the on-site conditions.

[0043] Step 4: Cast the cap in batches outside the 1m range of the subway structure plane projection. See the attached Figure 4 .

[0044] The cast-in-place cap 5 outside the 1m range of the subway structure plane projection is divided into multiple caps from top to bottom, and the construction is carried out in batches from bottom to top. The cap adopts modular reinforcement technology, and the cap steel bars of the adjacent two parts adopt rapid connection technology (such as mechanical sleeves, etc.).

[0045] Step 5: Hoist the prefabricated cap 6 within 1m of the subway structure plane projection. See attached for details. Figure 5 .

[0046] The pedestals within 1m of the plane projection of the subway structure are prefabricated and hoisted as a whole.

[0047] Step 6: Construction of wet joints 7 of the foundation, see the attached Figures 6 to 8 .

[0048] The cast-in-place cap 5 and the prefabricated cap 6 are connected quickly. The main reinforcement of the cap is fixed by welding through the reserved U-shaped steel bars (wet joint steel bars 8) arranged crosswise, and Φ10 steel bars are passed through the middle. After the steel bars are welded and fixed, UHPC9 or high-strength concrete is used for pouring construction.

[0049] Step 7: Prestressing and backfilling of the foundation.

[0050] Preferably, the subway structure monitoring during the construction process adopts a fully automatic vibration monitor 10 in the subway shield for vibration monitoring, and at the same time, data on shield settlement and convergence are regularly collected inside the subway shield. Based on the monitoring and collected data, timely feedback is given and a series of response mechanisms such as data feedback, data analysis, and optimization of subsequent processes and technologies are established.

[0051] This construction method can avoid damage to the existing operating subway structure during the construction of the pedestal and greatly reduce the disturbance of the pedestal to the subway. It utilizes the combination of pile foundation pull-out resistance, cast-in-place pedestal and prefabricated pedestal technology and pedestal rapid splicing technology to effectively prevent the subway shield from floating up, vibration and breakage, etc. It also has the advantages of avoiding large-volume concrete pouring, flexible and controllable overall process, rapid construction of the pedestal directly above the subway, and timely adjustment of subsequent processes based on subway monitoring data.

[0052] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for constructing a large-volume foundation directly above an existing operating subway, characterized in that: By using short piles for enclosure, controlling the depth of pit bottom soil reinforcement, dividing cast-in-place caps, combining cast-in-place caps with prefabricated caps, and rapid cap splicing, the construction of a large-volume cap directly above the existing operating subway can be achieved. The specific steps are as follows: Step 1: Set up the detection device in the subway shield and collect the initial value; Step 2: Construction of foundation pit support; Step 3: Strengthen the bottom of the foundation pit; Step 4: Cast the cap in batches outside the 1m range of the subway structure plane projection; Step 5: Hoist the prefabricated cap within 1m of the plane projection of the subway structure; Step 6: Wet joint construction of the foundation; Step 7: The foundation is tensioned and backfilled in batches.

2. The method for constructing a large-volume foundation directly above an existing operating subway according to claim 1, characterized in that: In step 2, short piles are used for enclosure within 1m of the plane projection of the subway structure to ensure that the existing subway operation is not affected. The enclosure piles can be one or more combinations of Larsen steel sheet piles, bored piles, SMW method piles, and MJS method piles according to the site conditions.

3. The method for constructing a large-volume foundation directly above an existing operating subway according to claim 1, characterized in that: In step 3, the pit bottom reinforcement plane covers the entire pit to ensure that the soil reinforcement depth is determined without affecting the existing subway operation. The soil reinforcement adopts MJS reinforcement, grouting or triaxial mixing piles according to the site conditions.

4. The method for constructing a large-volume foundation directly above an existing operating subway according to claim 1, characterized in that: In step 4, the pedestal outside the 1m range of the subway structure plane projection is divided into multiple pedestals from top to bottom, and the construction is carried out in batches one by one from bottom to top.

5. The method for constructing a large-volume foundation directly above an existing operating subway according to claim 1, characterized in that: In step 5, the pedestal within the 1m range of the subway structure plane projection is constructed by integral prefabrication and hoisting.

6. The method for constructing a large-volume foundation directly above an existing operating subway according to claim 1, characterized in that: In step 6, the cast-in-place cap and the precast cap are quickly connected, the main reinforcement of the cap is fixed by welding through the reserved cross-arranged U-shaped steel bars, and Φ10 steel bars are passed through the middle. After the steel bars are welded and fixed, UHPC or high-strength concrete is used to construct the wet joint of the cap.

7. The method for constructing a large-volume foundation directly above an existing operating subway according to any one of claims 1 to 6, characterized in that: The subway structure monitoring during the construction process adopts the fully automatic vibration monitoring device inside the subway shield to carry out vibration monitoring. At the same time, the shield settlement and convergence data are regularly collected inside the subway shield. According to the monitoring and collection data, timely feedback is given and a series of response mechanisms are established for data feedback, data analysis, and optimization of subsequent processes and technologies.

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